已知xy=9,x-y=-3,求a^2+3xy+y^2的值
问题描述:
已知xy=9,x-y=-3,求a^2+3xy+y^2的值
答
x²+3xy+y²
=(x²-2xy+y²)+5xy
=(x-y)²+5xy
=(-3)²+5×9
=9+45
=54